cheap/chinese LPSU's - minefield?

[the_doc735]

3 minutes ago, jabbr said:

 

You need to figure this out before you can begin to build a power supply.

 

There is no "one right answer -- it depends on the board you select. 

 

Draw a schematic of the circuit you are planning -- there is no one answer, it depends on the design you select.

 

If you need help, look up examples of linear power supply designs on the web. There are many examples.

can;t the board seller tell me the input voltage? If yes? I will write to them again and wait.

[the_doc735]

41 minutes ago, the_doc735 said:

can;t the board seller tell me the input voltage? If yes? I will write to them again and wait.

This board was recommended by @look&listen , he has been using it for nine months with no issues.

https://www.ebay.co.uk/itm/131588996943?ul_noapp=true

 

...maybe he knows the input voltage?

[Superdad]

1 hour ago, the_doc735 said:

can;t the board seller tell me the input voltage? If yes? I will write to them again and wait.

 

That's really not the issue.  For input, a couple of volts above the voltage that the output regulator is set to will be fine--but that has to be the case even when the supply is under full load (the trans. mfr. will usually specify the voltage as loaded).  The issue is calculating the post-diode transformer secondary voltages, specifying their current, and making sure that that when the board is fed a much higher voltage (which will happen when under light or medium load), it is able to take that and that you have ability to sink the heat from whatever drop there is.

 

Sorry that you took offense, but asking that Chinese board seller the input voltage is bit like asking the mechanic "how tight do I make all the bolts?" or the chef "what is the best sauce to use?"  It all depends...  

[sandyk]

 

 

Quote

...maybe he knows the input voltage?

The Input voltage will of course depend on the chosen Output Voltage, which also means that the transformer as well will need to be selected to provide adequate, but not too much headroom for the selected output voltage.

 You will need to ask these questions of the vendor when selecting the voltage version and current required.

[davide256]

I have one of those cheap chinese LPS's, works ok as an upgrade for my turntables 24vDC transformer. But the voltage does drift  up to .5V higher and it becomes unstable

if you turn the voltage adjustment screw below 12V...

[jabbr]

2 hours ago, the_doc735 said:

This board was recommended by @look&listen , he has been using it for nine months with no issues.

https://www.ebay.co.uk/itm/131588996943?ul_noapp=true

 

...maybe he knows the input voltage?

 

I understand, and no doubt he has it working, but you are the one who wants to use it to design a new product and you are the one who needs the answer. If you can't get the answer then either figure it out or use something else. The advantage for you of buying a product that is complete is that you don't need to answer these questions (of course you won't learn that way either) but if you do want to learn there is a whole wide internet at your fingertips that will enable you to answer these questions.

 

(I don't own, have never built nor want a linear powered ATX supply because I focus on low powered boards/streamers next to my DACs)

[jabbr]

5 hours ago, Superdad said:

Well not only that, but most transformer manufacturers quote the AC output voltage of their secondaries at the max current rating for that winding.  At lower loads the voltage is going to be a lot higher so consideration (and calculation of rectified DC voltage levels) of that  comes in right away, lest the regulator board gets forced to handle a rather large drop.

 

 

Baby steps, baby steps ... that's why its called the "Burning Amp" festival  

 

But ... slightly larger drop and lower amps generally is still lower wattage the heatsink needs to dissipate ?‍♂️

 

[Superdad]

50 minutes ago, jabbr said:

 

Baby steps, baby steps ... that's why its called the "Burning Amp" festival.

 

Burning Amp, Burning Man.... Due to my thinning pate I recently came up with an idea for a party festival for middle-aged men, to be held not in the desert but someplace rather shady like an Oregon forest.   It’s going to be called “Balding Man.”  Sponsors will include Rogaine and there will be booths selling dome polish and contests for best combover, etc.. 

 

50 minutes ago, jabbr said:

But ... slightly larger drop and lower amps generally is still lower wattage the heatsink needs to dissipate .

 

Of course.  I sometimes forget how easy just one output voltage target per secondary would be—since we build a wide-range, (5-12V / 5-7.2A) supply off a single 21V (unloaded) secondary.  Much cooler at 12V than at 5V! 

[look&listen]

1 hour ago, jabbr said:

3 hours ago, the_doc735 said:

This board was recommended by @look&listen , he has been using it for nine months with no issues.

https://www.ebay.co.uk/itm/131588996943?ul_noapp=true

 

...maybe he knows the input voltage?

 

I understand, and no doubt he has it working

 

No, not recommend PCB, only provide link. Not build from it, but buy complete LPSU, so not have to worry about those voltages (only needed output v). But have made little LPSU from modules. Not too hard, but experience & research helpful.

Sorry, but no patience to spoon feed through scatter shot questions. Maybe he try DIYAudio.com?

[jabbr]

28 minutes ago, Superdad said:

Burning Amp, Burning Man.... Due to my thinning pate I recently came up with an idea for a party festival for middle-aged men, to be held not in the desert but someplace rather shady like an Oregon forest.   It’s going to be called “Balding Man.”  Sponsors will include Rogaine and there will be booths selling dome polish and contests for best combover, etc.. 

 

 

Too much hair? ... what lab supplies are those?

 

Also what values of SuperCaps for your combovers? 3 way?

[sandyk]

3 hours ago, davide256 said:

I have one of those cheap chinese LPS's, works ok as an upgrade for my turntables 24vDC transformer. But the voltage does drift  up to .5V higher and it becomes unstable

if you turn the voltage adjustment screw below 12V...

 

Any LPS whose output voltage drifts by 500mV is NOT well designed.

A typical drift with temperature and load conditions should be more like 10% (or less) of that.(< + and - 50mV)

 The output voltage of most voltage regulators increases a little with increasing temperature, and the output voltage droops a little with higher current loads.

[the_doc735]

17 hours ago, Superdad said:

 

That's really not the issue.  For input, a couple of volts above the voltage that the output regulator is set to will be fine--but that has to be the case even when the supply is under full load (the trans. mfr. will usually specify the voltage as loaded).  The issue is calculating the post-diode transformer secondary voltages, specifying their current, and making sure that that when the board is fed a much higher voltage (which will happen when under light or medium load), it is able to take that and that you have ability to sink the heat from whatever drop there is.

 

Sorry that you took offense, but asking that Chinese board seller the input voltage is bit like asking the mechanic "how tight do I make all the bolts?" or the chef "what is the best sauce to use?"  It all depends...  

So, the board supplier cannot help? Oh shit! And when you look at this pic:

..there really doesn't look all that much to it. Just 3 or 4 wires in/out of tranny to a board with cap array and regulators (& rectifiers), couple of sockets and a switch. Not very good on the academic (maths/physics) side of things; more practical hands on learning and experimenting. People are concerned about me messing with mains electric appliances but I always drain large storage caps etc before my hands go in and test with DMM to make sure it is safe to proceed. I have had my hands on electronics for 42 years + in a basic way, AND I'M STILL ALIVE! LOL! Just super cautious I suppose? B.T.W. I have tried just about every cooking sauce in TESCO (UK) and YES! ..some I like better than others and have even added my own ingredients to alter the taste! As for how tight the bolts are, crucial ones are on the cylinder head, brakes and steering. The engines I have worked on luckily all have specification charts detailing the torque required, so you just set the torque wrench to those parameters and away you go! It gets a bit more technical when someone asks you to re-profile a camshaft for greater lift to increase the engine power. You then need precision engineering lathes to dial in the new profile on the cutter. Same when increasing piston barrel size for more power so that you can put larger pistons in the barrels. Of course, that usually means gas flowing and porting the head otherwise you are wasting your time, like wise with better air filters, exhausts & fuel pumps, Oh! and timing. I like nelson pass type analogies, when he tries to explain electronics using and comparing it to hydraulics, water flow and damns.

[the_doc735]

17 hours ago, sandyk said:

 

 

The Input voltage will of course depend on the chosen Output Voltage, which also means that the transformer as well will need to be selected to provide adequate, but not too much headroom for the selected output voltage.

 You will need to ask these questions of the vendor when selecting the voltage version and current required.

I know I need power to cover the 3.3, 5, 12 + 12v input on the mobo. Surely that has to be spot on e.g. I can't have 5, 9, 15, 18v? I know the amps should be above the required draw (obviously not below!). So, 1 [or 2] A would be OK for say 0.6A appliance draw? But I don't know the load/amperage on those four individual voltages! I know the whole computer uses about 62W peak at boot up, but then drops back to around 32/33W after boot (using a meter). Thanks.

[the_doc735]

15 hours ago, jabbr said:

 

I understand, and no doubt he has it working, but you are the one who wants to use it to design a new product and you are the one who needs the answer. If you can't get the answer then either figure it out or use something else. The advantage for you of buying a product that is complete is that you don't need to answer these questions (of course you won't learn that way either) but if you do want to learn there is a whole wide internet at your fingertips that will enable you to answer these questions.

 

(I don't own, have never built nor want a linear powered ATX supply because I focus on low powered boards/streamers next to my DACs)

can you give any example links where I won't just end up at another forum asking the same questions and left baffled. There's no point in just asking this again on another forum, only to end up yet again at the same place. Cheers!

[the_doc735]

14 hours ago, look&listen said:

 

No, not recommend PCB, only provide link. Not build from it, but buy complete LPSU, so not have to worry about those voltages (only needed output v). But have made little LPSU from modules. Not too hard, but experience & research helpful.

Sorry, but no patience to spoon feed through scatter shot questions. Maybe he try DIYAudio.com?

Yes, I understand if you don't wish to hand hold, that's OK. I just thought you said you had no problems with this PCB for nine months in use? Ah Ah! tried DIYAudio quite a while ago and they said "we don't teach, buy a book".

Cheers!

[the_doc735]

14 hours ago, jabbr said:

 

Too much hair? ... what lab supplies are those?

 

Also what values of SuperCaps for your combovers? 3 way?

Ah ah, good laugh!! I'm a baldy too!

[jabbr]

13 minutes ago, the_doc735 said:

Ah Ah! tried DIYAudio quite a while ago and they said "we don't teach, buy a book".

Cheers!

 

I think that’s good advice. The question I asked you was very very basic and if you aren’t able to answer it, why do you expect people to answer these questions for you? — yes you should get an introductory electronics textbook and read it. Or take a class at a local university or community college or hire a tutor. You need to make some effort to educate yourself.

 

Or not.

 

and don’t tell me that you already know about electronics because you’ve been doing it for 42 years because if you understood what you were doing you could figure out what transformer you need.

[the_doc735]

17 minutes ago, jabbr said:

 

I think that’s good advice. The question I asked you was very very basic and if you aren’t able to answer it, why do you expect people to answer these questions for you? — yes you should get an introductory electronics textbook and read it. Or take a class at a local university or community college or hire a tutor. You need to make some effort to educate yourself.

 

Or not.

 

and don’t tell me that you already know about electronics because you’ve been doing it for 42 years because if you understood what you were doing you could figure out what transformer you need.

OK OK, keep your hair on mate LOL!

Can't do course at college, mainly housebound and incontinent these days. Need several tablets and injections per day just to stay alive. However, can learn at home remotely from college or books.

[jabbr]

There are many online tutorials.

[Ralf11]

I'm sorry to hear about your medical issues.  Besides online, I'm sure there are Dummies Guides in electricity, electronics, etc.  - maybe even in transformer design.

[the_doc735]

33 minutes ago, Ralf11 said:

I'm sorry to hear about your medical issues.  Besides online, I'm sure there are Dummies Guides in electricity, electronics, etc.  - maybe even in transformer design.

medical issues suddenly got  a lot worse 7 years ago, before that only slight disability. Would now need car with adaptive controls if I was driving. Oh well, never mind, mainly self sufficient, with a little home help (LOL!). Thanks for saying! 

Don't suppose it's worth me asking any more questions about building LPSU's? (on here)?

Interestingly just got a reply from the LPSU board supplier in china and UNLIKE the tranny supplier has offered to help a little bit with voltage input. He mentions the same issues as @jabbr  and @Superdad  and @sandyk . So answered his questions and wrote back! Waiting now!

[Ralf11]

the real issue here is that an LPS is not always better than a SWPS - I like to let competent engineers design my gear (unless it is some oddball scientific instrument no one has gotten around to yet)

 

BTW, a self-driving car for you is just a year or two away

[sandyk]

2 hours ago, the_doc735 said:

Interestingly just got a reply from the LPSU board supplier in china and UNLIKE the tranny supplier has offered to help a little bit with voltage input. He mentions the same issues as @jabbr  and @Superdad  and @sandyk 

 

Among the other unanswered questions that really need to be known, is how much is the required minimum voltage differential between the Input and Output voltages. This particular PSU PCB design is not like when using a quoted type voltage regulator I.C.  (LM3xx , or a L.D.O type etc.) where we know the minimum voltage differential for proper regulation.

You also need to know the amount of maximum current as well as the rectified voltage from the transformer you will be using to determine the heat sinking requirements from the amount of heat to be dissipated.

( My 15W Ch. Class A amplifier for example, dissipates a total of over 80W [P =E x I ] of heat and requires a 300mm x 75mm x 49mm (W x H x D) heatsink on either side of the 2U rack case for safe operation in the hotter months.)

 Obviously, the higher the Input -Output voltage differential and the high current that this PSU PCB is capable of will determine the amount of heat sinking required.

 You would more than likely be using a Bridge Rectifier configuration, and the attached chart will assist with working out the voltages to be expected from a particular transformer and rectifier combination with a large value filter capacitor.

[the_doc735]

3 hours ago, Ralf11 said:

the real issue here is that an LPS is not always better than a SWPS - I like to let competent engineers design my gear (unless it is some oddball scientific instrument no one has gotten around to yet)

 

BTW, a self-driving car for you is just a year or two away

Yes, people do say that SMPS is not always bad, but percentage wise there seems to be twice as many votes for LPS in audio gear. And of course the vendors like to "blow their own trumpets". There are pros and cons to both, and I suspect everyone hears a little different anyway. I know that when I went from a mediocre SMPS to a flagship SMPS the better sound was immediately obvious (no blind fold needed!). I guess I'm hoping for the same level of improvement by shifting to a LPSU?

Umm? don't know if I'd trust A.I. autocars! (LOL). Think I'll stick to push/pull accelerator & brake! When I get licence back.

[the_doc735]

2 hours ago, sandyk said:

 

Among the other unanswered questions that really need to be known, is how much is the required minimum voltage differential between the Input and Output voltages. This particular PSU PCB design is not like when using a quoted type voltage regulator I.C.  (LM3xx , or a L.D.O type etc.) where we know the minimum voltage differential for proper regulation.

You also need to know the amount of maximum current as well as the rectified voltage from the transformer you will be using to determine the heat sinking requirements from the amount of heat to be dissipated.

( My 15W Ch. Class A amplifier for example, dissipates a total of over 80W [P =E x I ] of heat and requires a 300mm x 75mm x 49mm (W x H x D) heatsink on either side of the 2U rack case for safe operation in the hotter months.)

 Obviously, the higher the Input -Output voltage differential and the high current that this PSU PCB is capable of will determine the amount of heat sinking required.

 You would more than likely be using a Bridge Rectifier configuration, and the attached chart will assist with working out the voltages to be expected from a particular transformer and rectifier combination with a large value filter capacitor.

 

WOW! many thanks for the diagram. Too much to answer.

 

"Among the other unanswered questions that really need to be known, is how much is the required minimum voltage differential between the Input and Output voltages." This is what the PCB supplier also said straight away, just like superdad & jabbr. The PCB supplier in china thinks he can help just by me telling him the specs. of my ITX PC. He also sells tranny's and can match them up with the PCB's, for my PC inputs! At this stage he asks if I am attempting to build LPSU myself to save on costs? I said: "yes". There's a chance he could supply it in kit form thus deducting labour charges for final assembly. Either with the PCB's fully built OR just component style with diagrams, and all I would have to do then is fix it all together "MONKEY STYLE" (not sex!) i.e. 'spanner'/parrot fashion!

 

"This particular PSU PCB design is not like when using a quoted type voltage regulator I.C.  (LM3xx , or a L.D.O type etc.) where we know the minimum voltage differential for proper regulation." Oh bloody hell, trust me to pick something that is not standard. I suppose the r-core physics is more complex than Toroidal as well?

 

"You also need to know the amount of maximum current as well as the rectified voltage from the transformer you will be using to determine the heat sinking requirements from the amount of heat to be dissipated." Well, massive alloy case with fins to dissipate heat! (LOL) think I need the "for dummies" volume right now. This will take longer than I foresaw!!

 

Well, this is a real eye opener for me, never realized there was so much to matching/balancing a PCB with a tranny! I've just been swapping out dead parts to fix them all these years with elementary knowledge. Not building or designing appliances!

 

Thanks for the 'heads up'!